Thermoregulation

Question 1

What is Thermoregulation?

Answer 1

Thermoregulation refers to maintaining the balance between heat loss and heat gain, the average human body is 36.8 degrees, heat gained must equal heat loss

Question 2

What is the Body’s Heat Inputs?

Answer 2

• Heat gained from body processes (metabolism) and especially respiration of liver and muscle cells
• Heat gained from surroundings by conduction and radiation

Question 3

What is the Body’s Heat Outputs?

Answer 3

• Evaporation of water from skin and lungs, warm air breathed out, warm urine and warm faeces
• Heat lost through radiation, conduction, convection to surroundings

Question 4

What are Tolerance Limits?

Answer 4

• Tolerance limits are the upper and lower limits to a range of factors
• Within these limits the body function normally
• A rise above or fall below the normal range means that the individuals tolerance limits have been exceeded and dysfunctions will occur
• Hypothermia - extreme cold conditions
• Hyperthermia - extreme heat conditions, death can

Question 5

What are the methods of heat transfer ?

Answer 5

• Conduction (heat transferred to another by direct contact)
• Convection (heat transferred through convection currents)
• Radiation (heat transferred without physical contact)
• Evaporation (heat transferred by the conversion of a liquid to a vapour e.g. sweating)

Question 6

What are the body’s Temperature Receptors?

Answer 6

1. Peripheral Thermoreceptors: cold and hot, those in the skin and mucous membranes
2. Central Thermoreceptors: located in the Hypothalamus

Question 7

What factors affect Metabolic Rate?

Answer 7

1. Exercise - leads to increased muscle activity which increases the metabolic rate by 40%, thus increasing heat production
2. Stress - arises stimulation of sympathetic nervous system, which releases noradrenaline and increases the metabolic rate of the cells which leads to an increase in heat production
3. Rising body temperature - leads to increased metabolic activity (for each 1 degree rise the rate of metabolic reactions increased by 10%)

Question 8

How is the skin involved in Temperature Regulation?

Answer 8

• Changes in the skin can speed up or slow down the rate at which heat is lost from the body
• Blood vessels carry heat to the skin from the core of the body and heat can then be lost from the skin by conduction, convention, radiation and evaporation
• If large amounts of heat need to be lost sweating can occur, sweating is the active secretion of fluid by the sweat glands and periodic contractions of cells surrounding the ducts, to pump the sweat to the skin surface stimulated by the sympathetic nerves

Question 9

What are the ways the body can maintain heat?

Answer 9

1. Vasoconstriction - decreases the heat transfer from internal organs to skin
2. Stimulation of Adrenal Medulla - secretion of adrenaline and noradrenaline to increase metabolic rate and heat production
3. Shivering - under control of hypothalamus
4. Increase in thyroxine - causes AN love to secrete TSH which causes the thyroid to release thyroxine and thus increase metabolic rate increasing heat
5. Behavioural response - putting on a jumper or curling up in a ball

Question 10

What are the ways in which the body looses heat?

Answer 10

1. Vasodilation - increases blood flow through the skin, heat is lost through radiation and convection
2. Sweating - needed to increase heat loss from the body, has a cooling affect
3. Decrease in Metabolic Rate - reduction in the secretion of thyroxine to reduce heat production
4. Behavioural Response - turning on air conditioner, removing clothing